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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef UI_EVENTS_EVENT_DISPATCHER_H_
#define UI_EVENTS_EVENT_DISPATCHER_H_
#include "base/auto_reset.h"
#include "ui/events/event.h"
#include "ui/events/event_constants.h"
#include "ui/events/event_handler.h"
#include "ui/events/events_export.h"
namespace ui {
class EventDispatcher;
class EventTarget;
class EventTargeter;
struct EventDispatchDetails {
EventDispatchDetails()
: dispatcher_destroyed(false),
target_destroyed(false) {}
bool dispatcher_destroyed;
bool target_destroyed;
};
class EVENTS_EXPORT EventDispatcherDelegate {
public:
EventDispatcherDelegate();
virtual ~EventDispatcherDelegate();
// Returns whether an event can still be dispatched to a target. (e.g. during
// event dispatch, one of the handlers may have destroyed the target, in which
// case the event can no longer be dispatched to the target).
virtual bool CanDispatchToTarget(EventTarget* target) = 0;
// Returns the event being dispatched (or NULL if no event is being
// dispatched).
Event* current_event();
// Dispatches |event| to |target|. This calls |PreDispatchEvent()| before
// dispatching the event, and |PostDispatchEvent()| after the event has been
// dispatched.
EventDispatchDetails DispatchEvent(EventTarget* target, Event* event)
WARN_UNUSED_RESULT;
protected:
// This is called once a target has been determined for an event, right before
// the event is dispatched to the target. This function may modify |event| to
// prepare it for dispatch (e.g. update event flags, location etc.).
virtual EventDispatchDetails PreDispatchEvent(
EventTarget* target,
Event* event) WARN_UNUSED_RESULT;
// This is called right after the event dispatch is completed.
// |target| is NULL if the target was deleted during dispatch.
virtual EventDispatchDetails PostDispatchEvent(
EventTarget* target,
const Event& event) WARN_UNUSED_RESULT;
private:
// Dispatches the event to the target.
EventDispatchDetails DispatchEventToTarget(EventTarget* target,
Event* event) WARN_UNUSED_RESULT;
EventDispatcher* dispatcher_;
DISALLOW_COPY_AND_ASSIGN(EventDispatcherDelegate);
};
// Dispatches events to appropriate targets.
class EVENTS_EXPORT EventDispatcher {
public:
explicit EventDispatcher(EventDispatcherDelegate* delegate);
virtual ~EventDispatcher();
void ProcessEvent(EventTarget* target, Event* event);
const Event* current_event() const { return current_event_; }
Event* current_event() { return current_event_; }
bool delegate_destroyed() const { return !delegate_; }
void OnHandlerDestroyed(EventHandler* handler);
void OnDispatcherDelegateDestroyed();
private:
void DispatchEventToEventHandlers(EventHandlerList* list, Event* event);
// Dispatches an event, and makes sure it sets ER_CONSUMED on the
// event-handling result if the dispatcher itself has been destroyed during
// dispatching the event to the event handler.
void DispatchEvent(EventHandler* handler, Event* event);
EventDispatcherDelegate* delegate_;
Event* current_event_;
EventHandlerList handler_list_;
DISALLOW_COPY_AND_ASSIGN(EventDispatcher);
};
} // namespace ui
#endif // UI_EVENTS_EVENT_DISPATCHER_H_
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